1. Field
This invention relates to mechanical chairs of the type used by providers of professional services, and is particularly directed to such chairs having chair backs that pivot relative to chair seats.
2. Art
Many personal service professions, such as those providing personal grooming, physical therapy, medical and dental services, utilize chairs which are mechanically adjustable. The back of such a chair typically pivots with respect to an associated seat. It is common for chair back and seat arrangements of this kind to be mounted on a pedestal base and to be associated with apparatus for adjusting the elevations and relative positions of the chair seat and back. Dental patient chairs are representative of this class of personal services chair.
Certain personal services chairs are arranged so that the chair seat supports the entire lower body of an individual. The seat moves longitudinally as the chair back is pivoted with respect to the chair seat. Relative movements of the seat and back can cause discomfort to one seated in the chair, particularly as the chair is "reclined."
For example, as a dental patient chair back rotates with respect to the chair seat, the patient in the chair may feel stretched or compressed to some degree. This sensation occurs because the rotation of the chair back about a fixed pivot point relative to the seat back actually does slightly stretch or compress the lower portion of the body relative to the upper part of the body. Unless the patient repositions his body in the chair during such movement, he may experience some discomfort or irritation. In an operatory environment, it is important to avoid imposing stresses of this kind on a patient.